1. Technical Field
The disclosure relates to a semiconductor device. More particularly, the disclosure relates to a metal oxide semiconductor transistor.
2. Description of Related Art
Metal oxide semiconductor transistor is a transistor using metal oxide semiconductor layer to be its active layer. Comparing with those transistors using amorphous silicon layer as their active layers, the metal oxide semiconductor transistors have higher charge carrier mobility. While comparing with those transistors using low-temperature polysilicon layer as their active layers, the metal oxide semiconductor transistors have simpler manufacturing process and more uniform metal oxide semiconductor layers to make the metal oxide semiconductor transistors have better performance.
At the present time, increasing the mobility of the charge carriers is a method to further improve the performance of the transistors. One of the common ways is to crystallize the transistor's active layer to form a polycrystalline structure. For example, the transistors using polysilicon layer to be the active layer can have higher charge carriers mobility. However, the formation of the polysilicon increases the difficulty of the manufacturing process, and the non-uniformity of the polysilicon layer decreases the performance of the transistor. Besides, changing the material of the active layer is another way to increase the mobility of the transistors' charge carrier, but the R&D difficulty for finding new replaceable materials is also increased. Therefore, it is unfavorable to increase the improving rate of the transistors' performance.